igneous
Vesicular Basalt (Amygdaloidal Basalt)
Extrusive Mafic Igneous Rock
Hardness: 5-6 (Mohs); Color: Dark brown to black; Luster: Dull to sub-metallic (shiny when wet); Structure: Aphanitic with vesicles (gas bubbles); Cleavage: None
- Hardness
- 5-6 (Mohs)
- Color
- Dark brown to black
- Luster
- Dull to sub-metallic (shiny when wet)
Identified More igneous →
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Physical properties
Hardness: 5-6 (Mohs); Color: Dark brown to black; Luster: Dull to sub-metallic (shiny when wet); Structure: Aphanitic with vesicles (gas bubbles); Cleavage: None
Formation & geological history
Formed from the rapid cooling of magnesium-rich and iron-rich lava at or near the Earth's surface. The pits (vesicles) are created by trapped gas bubbles escaping as the lava cools.
Uses & applications
Commonly used as aggregate for road construction, railroad ballast, and landscaping. Small, water-worn pebbles are often collected as river stones.
Geological facts
Basalt is the most common rock type in the Earth's crust and makes up most of the ocean floor. It is also found on the Moon and Mars.
Field identification & locations
Identify by its dark color, heavy weight (high density), and the presence of small holes or pits. Commonly found in volcanic regions, riverbeds, and glacial deposits.
